I built my team's current CAD computer using parts from our mentor's company (they were moving over to new PCs).
Specs:
OS: Win 10 64bit
RAM: 16GB 1333MZ (DDR3)
CPU: AMD FX-6300 (with a CoolerMaster 212
)
GPU: AMD 6970
HDD: 1 1TB drive and 1 500 Gig Drive
SSD: Boot Drive and one 64gig CAD drive.
PSU: 800 watts
Case: MASSCOOL CS-ICS8200 (It has a built in AC. That's right, an AC!)